Beveled vs. Non-Beveled Gingival Margins in Class II Composite Preparations

Objectives: To compare the in–vitro microtensile enamel adhesive bond strength of four adhesives to beveled vs non-beveled gingival margins of class II resin composite preparations. Methods: After IRB approval, twenty-six extracted human third molars were randomly distributed into four adhesive treatment groups; (Clearfil-SE (self-etch), Excite (total-etch), PQ1 (total-etch) and Filtek-LS (self-etch, silorane based)). Each tooth received two class II preparations with half of its gingival margin beveled and the other half not beveled.  After adhesive placement three increments of resin composite (Z250-3M-ESPE^TM) were added for all groups except Filtek-LS, which was restored with Silorane resin composite.  Materials were cured with a quartz halogen light per manufacturer’s instructions.  Twenty-four hours later teeth were sectioned to obtain rectangular specimens with a surface area of approximately 0.5 mm².  Samples were tested on a Bisco microtensile tester at a crosshead speed of 2.0mm/min.  A light microscope (50x) was used to characterize modes of failure as adhesive or cohesive.  Debonded samples during specimen preparation were not included in strength values.

Results:

A two-way ANOVA found a statistically significant difference between adhesives (p≤0.001).  A post-hoc TukeyHSD found Filtek-LS was significantly weaker than the other adhesives (p≤0.05). Beveled enamel had greater bond strengths than non-beveled enamel.  Chi-squared showed non-beveled margins had more debonds than beveled margins for Excite (N=30, Χ²=10.0) and Filtek-LS; (N=26, Χ²=8.21), p<0.0125.

Conclusion: Beveled enamel had greater bond strengths than non-beveled enamel in class II resin composites. Silorane adhesive gave reduced bond strengths compared to  Bis-GMA adhesives. Funded in part by USPHS Grant K23-DE016324. purkj@umkc.edu